Thousands of junior doctors will start their new jobs today - a day which has been known as "black Wednesday" in the past because it has been linked to higher death rates among patients.

Studies have previously linked the first Wednesday in August, the day when freshly-qualified doctors arrive on hospital wards, to a rise in deaths.

This day also coincides with a changeover in the training schedules of junior medics who have already been working in the hospital.

Reports suggest that mortality rates rise by around 6% as new trainees start work and others change rotations.

A new poll of junior doctors already working in hospitals across the UK found that the majority do not feel as though they have enough time to care for patients.

Of the 1,000 training medics polled by the Medical Protection Society, 70% said they feel as though they do not have enough time to give patients the care they need.

And half said that they had concerns about quality of care in their workplace.

Meanwhile, 82% said they struggled with long hours in the last year and almost two thirds said they had difficulty with heavy workloads. One in 20 junior medics said that they had been forced to have time off work due to stress.

Earlier this year, medical experts said that staggering junior doctors' training rotations could help to prevent the ''black Wednesday'' phenomenon.

The Academy of Medical Royal Colleges recommended that while all Foundation Year 1 - junior doctors in the first year of the programme which forms the bridge between medical school and specialist training - should commence work on the first Wednesday in August, junior doctors already working in hospitals should not change over departments until September.

The Academy said that this will mean that the newest doctors will always work with trainees who have already been doing the job for a number of months.

This, on top of an existing scheme whereby newly qualified doctors ''shadow'' senior colleagues for the first few days, should help to address the issue, an Academy spokeswoman said.

In 2012, the Department of Health announced the s hadowing programme for junior doctors to ensure that medical graduates are supported as they make the transition from university to their first full employment as doctors.

A spokeswoman for Health Education England said: "Patient safety is paramount for Health Education England and we welcome the fact that there is shadowing now in place for all trainees."

Dr Pallavi Bradshaw, medico-legal adviser at the Medical Protection Society, said: "Junior doctors struggling with long hours is not a new problem. What is of concern is that 70% felt that a lack of time compromised the care they gave to patients.

"This highlights the need for junior doctors to be supported by senior clinicians and management during this challenging stage in their career."

Commenting on the poll, Dr Andrew Collier, co-chair of the British Medical Association's (BMA) Junior Doctors Committee, said: "It's vitally important that junior doctors feel supported and encouraged to speak out about concerns over patient care.

"It's really worrying that so many junior doctors feel they don't have enough time to give patients the care they need and that many have had to raise concerns over the quality of care. This shows that rising workloads are becoming a real barrier to patient care."

He added that the shadowing scheme means that new doctors feel "more confident and less anxious".

"The introduction of a shadowing scheme in recent years, which was long fought for by the BMA, means new doctors are better prepared on their first day by being familiar with a hospital's systems, including everything from ordering tests, to filling in paper work," he said.

"This ensures patients continue to receive the best possible care, whatever day of the year it is, and leaves new doctors feeling more confident and less anxious.

"New doctors still have to face the reality of excessive hours and workloads, however, which can leave them exhausted and potentially compromise patient care, and despite recent improvements in patient safety brought about by shadowing, trusts still need to do more to make junior doctors feel that they are a valued part of the healthcare team.

"The BMA is currently in talks with NHS Employers over a new contract for junior doctors that we believe could help address problems around workload pressures, changeover and training, benefiting both patients and new doctors."

A Department of Health spokesman said: "New doctors have a long and rigorous training and induction process before starting work. We recently introduced better support for junior doctors and recent studies have found more than 95% go on to have long and rewarding careers."